Technical Field
The present disclosure relates to methods of disinfecting a fluid. More specifically, the present disclosure relates to a method of disinfecting a fluid by photo-catalytic deactivation of microbial organisms in the presence of a photo-catalyst comprising tungsten trioxide nanoparticles (n-WO3) doped with palladium nanoparticles (n-Pd) and a light for photocatalysis.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, is neither expressly nor impliedly admitted as prior art against the present invention.
The Word Health Organization (WHO) reports two million deaths worldwide annually due to consumption of microbial organism-infected water. Disinfection of water is therefore critical for human health and the environment. Various chemical processes based on activated carbon, coagulation and multimedia sand filtration have been applied for removing the microorganism. However, these technologies only transfer the contaminated substances from the treated water to another material that requires additional treatments and/or disposal. Although cost-effective and efficient, chlorination leaves the residual chlorine, which is toxic, in the treated water.
Additionally, disinfection of water in an oil field, e.g. produced water, is crucial for the quality of oil and protection of oil production workers and equipment. For example, sulfate-reducing bacteria (SRB) are an anaerobic microorganism that uses sulfate instead of oxygen for respiration and can survive and multiply in low oxygen environments. SRB can convert sulfate or sulfite present in water to hydrogen sulfide (H2S), which combines with iron to form iron sulfide scale. SRB accumulation increases the corrosiveness of the water in the oil field, and leads to hydrogen blistering or sulfide stress cracking in the pipeline. The corrosion of iron by SRB is rapid, and unlike ordinary rust, is not self-limiting. Besides being a well-known agent for scale formation in the oil field installations, SRB can also lead to the degradation of oil quality with high sulfur content and souring. Thus, deactivation of SRB from the water produced in oil fields is needed to reduce the rust formation, the production of deadly hydrogen sulfide, radioactivity and the degradation of oil quality.
In order to control the growth of SRB, many methods, such as using bactericides, removing sulfate from water, applying caustic washing to eliminate H2S, and oxidizing H2S to elemental sulfur, have been tried. Most of the organic bactericides, such as formaldehyde, phenolic and quaternary amine compounds, glutaraldehyde, chlorine, and acrolein, are harmful to the environment and human health. Additionally, SRB become resistant to the bactericides with time, in spite of high doses and repeated use. A microbiological process of deactivating SRB has also been proposed, where another breed of bacteria, such as denitrifying bacteria and sulfide-oxidizing bacteria, is introduced to compete with SRB for organic nutrients and inhibit their growth, however, it has not produced the desired effect due to the complexity of the method.
It is thus an object of the present disclosure to provide a method of disinfecting a fluid, e.g. waste water, produced water in an oil field, and sour water from an oil refinery, and more generally, a hydrocarbon contaminated fluid, by photo-catalytic deactivation of microbial organisms in the presence of a photo-catalyst comprising tungsten trioxide nanoparticles (n-WO3) doped with palladium nanoparticles (n-Pd) and a light for photocatalysis.